OIDC and SAML environment variables

[Varamil]

Added reference to all environment variables linked to OpenID and SAML configuration with a link to the documentation

Context

After a discussion on Grist Community forum, it has been suggested to update the list of environment variables.

Proposed solution

All environment variables linked to OpenID and SAML are missing in the readme file, I propose to add two lines referencing prefix GRIST_OIDC and GRIST_SAML respectively, and provide a link to the complete documentation with the full list for each.

Related issues

None

Has this been tested?

• 👍 yes, I added tests to the test suite
• 💭 no, because this PR is a draft and still needs work
• 🙅 no, because this is not relevant here (update of readme file)
• 🙋 no, because I need help

[fflorent]

First of all, thank you for your contribution and for taking care of this issue!

I agree that it would be more comfortable to mention the existence of the OIDC and SAML env variables in the README page.

I see that there exist sections for these variables: https://github.com/gristlabs/grist-core/blob/main/README.md#database-variables

I tend to think that:

• it could be more convenient to have these variables documented in a separate section dedicated to the authentication
• and like you just do, place links to the support website

What do you think?

[paulfitz]

Thanks a lot @Varamil !